Electromagnetic horn motor



March 5, 1957 J. MOSIER ,7

ELECTROMAGNETIC HORN MOTOR 1 Filed April 2'7, 1955 i J. MOS/ER INVENTORATTORNEYS United rates Patent ELECTROMAGNETIC HORN MOTOR Jacques Mosier,Ypsilanti, Mich, assignor to Ford Motor Company, Dearborn, Mich., acorporation of Delaware Application April 27, 1955, Serial No. 504,199 1Claim. (Cl. 318-134) This invention is concerned with an automotive hornand more specifically with a warning device in which the audible signalis produced by the vibrations of a metallic diaphragm which in turn isenergized by the oscillation of a buzzer or door bell type motor.

This invention is more particularly concerned with an improvement in theelectrical circuit of such a device. This particular improvement is bestunderstood by a study of the drawings in which:

Figure 1 is a section through a horn motor and;

Figure 2 is a section through a portion of the control apparatus for ahorn motor, and

Figure 3 is a circuit diagram of the electrical portion of the hornmotor.

Referring to Figure 1, diaphragm 10 is oscillated by slug 11 which inturn is attracted to post 12 when coil 13 is energized. The movement ofslug 11 towards post 12 under the influence of coil 13 causes slug 11 toimpart a vertical motion to pin 14 which in turn opens contact points 15which interrupt the current through coil 13 and permits slug 11 toreturn to the at rest position.

In the usual horn construction, contact points 15 are shunted by aresistor to lengthen the life of the contacts and suppress arcing. Thisresistor is objectionable because it permits a continuous partialenergization of coil 13 even when contact points 15 are open. Inasmuchas a horn works essentially upon differences in the flux intensity inthe magnetic circuit, the presence of this resistor requires aneedlessly heavy magnetic and electrical circuit to permit the fluxdensity to be raised above the norm established by the presence of theshunting resister.

The structure disclosed by this invention eliminates the usual resistorand substitutes therefore a selenium rectifier as is more clearly shownin Figure 3. In Figure 3, the contact points are again designated as 15,the coil is 13, and the selenium rectifier is designated as 16. Notethat rectifier 16 shunts coil 13 and not contact points 15. It will benoted that when the horn is energized, the current flows from positivepoint 17 through coil 13 through contact points 15 to negative point 18.Current flowing in this direction, that is the work ing current, isunable to flow through that portion of the circuit including seleniumrectifier 16. To properly practice this invention, it is essential thatthe active portion of the selenum rectifier be clamped against a cadmiumplated steel surface with sufiicient pressure to partially nullify itsinherent rectifier characteristics. For example, in a typical coil 12volt horn application of a forward voltage of about volts on theselenium rectifier considered apart from the coil should cause a currentof about 2% amperes to flow. Similarly a reverse voltage of 15 voltsshould cause not more than 0.25 ampere to flow. Ordinarily, this wouldbe considered a very poor rectifier. However, the instant contact points15 open, the inductance in coil 13 tends to continue the existing flowof current. This current now flows through selenium rectifier 16 in aforward direction and is dissipated by the ohmic resistance of thisrectifier. The dissipation of this energy in selenium rectifier 16preserves the contact points themselves from destruction by such energy.

In Figure 2, there has been shown a preferred example of a hornmechanism incorporating this invention. Here the upper contact point ofcontact points 15 is supported upon spring member 19. Beneath springmember 19 is insulator 20 through which the upper of contact points 15projects. Beneath insulator 20 is a rigid member 21 which supports thelower of contact points 15. Rigid member 21 is isolated by insulator 22.Upper plate 23 and rivets 24 serve to secure the entire assembly to thebody 25 which is, of course, at ground potential. Rectifier plate 26 issecured beneath upper plate 23 and clamped solidly in position by thepressure exerted by rivet 24. It is essential that the lower face ofupper plate 23 which is in contact with the rectifying surface ofrectifier 26 be cadmium plated and that rivet 24 exert suflicientpressure to nullify a portion of the rectifying action of this plate.This structure, illustrated in Figure 2, has been given as a typical andconvenient arrangement. However, it is to be understood that anyelectrical equivalent in which a selenium rectifier shunts coil 13 andin which the rectifying action of selenium rectifier 16 is partiallynullified by strong pressure against a cadmium plated surface may beused.

This apparently simple structure has resulted in a saving of 40% in thecurrent required to operate a horn and has extended the life of the hornat least 10 fold.

I have specifically disclosed a selenium rectifier as the propershunting mechanism for the horn contact points. However, other rectifiermeans may be used provided they present a substantial resistance to thefiow of current in the forward direction. This resistance must be largecompared to normal rectifiers to provide ohmic resistance to dissipatethe inductive energy of the coil.

It will be understood that the invention is not to be limited to theexact construction shown and described, but that various changes andmodifications may be made without departing from the spirit and scope ofthe invention, as defined in the appended claim.

I claim as my invention:

A buzzer type motor including an armature, a solenoid to propel saidarmature and contact points to interrupt the fiow of electrical currentthrough said solenoid, said solenoid being shunted by a seleniumrectifier in which the active face of the rectifier is clamped against acadmium plated metal plate under sufiicient pressure to partiallynullify the inherent rectifying properties of such rectifier, saidrectifier being polarized to permit current to flow as the magneticfield of the solenoid collapses.

References Cited in the file of this patent UNITED STATES PATENTS1,640,335 Grondahl Aug. 23, 1927 1,966,077 Nyman July 10, 1934 2,688,129Nielsen Aug. 31, 1954

